Are people animals?
Some animals like tigers and alligators are dangerous to own. They are wild and lethal.
Some animals would go extinct if they were allowed to own them. A list of these animals can be found below.
Certain dog breeds are aggressive and dangerous. Personality is a spectrum in dogs, some Labradors have worse personalities than terriers. A list of these breeds will need to be added here in a spectrum from worst to best. http://dangerousdogs.net/
Some people say there should be a dangerous owner act as there is no such thing as a dangerous dog.
History dangerous dog laws